The radiation characteristics of an antenna are typically determined by the communication system that it supports. An antenna may consist of a single radiator or may include many radiators acting in concert together to form a phased array. Examples of functionalities provided by phased array antennas include increased gain, conformality, sidelobe level (SLL) control, and electronic steering. The SLL is the decibel level difference between the peak of the biggest radiation lobe outside of the main antenna beam and the peak of the main beam itself.
A need has arisen for a SAR (synthetic aperture radar) antenna array that achieves high radiation efficiency while exhibiting low SLL performance. The low SLL requirement has been driven, for example, by the GMTI (Ground Moving Target Identification) mode of SAR operation, wherein the SAR uses the Doppler shift associated with a moving object to track that object's movement. It is therefore desirable to provide for such an antenna array.